The present disclosure relates to a system for the secondary suspension of a superstructure or a rail vehicle. The system includes a hydropneumatic spring unit as an active spring element which is placed between the superstructure and a bogie arranged below it and which ensures at least one raised traveling level NF for the superstructure when the rail vehicle is traveling.
In addition to the secondary suspension being used for the increase of comfort in the conveyance of passengers, a rail vehicle normally also has a primary suspension. The primary suspension acts between the wheel axles of the rail vehicle and the bogie and is used predominantly for absorbing hard shocks to which the rail vehicle is subjected during its travel as a result of an uneven rail guidance and the like. In contrast, a secondary suspension between a superstructure and railborne bogie of a rail vehicle is used for the additional vibration isolation of the superstructure in order to permit a particularly comfortable travel of the rail vehicle when conveying passengers. In many cases, the secondary suspension also interacts with a roll control for the superstructure.
From European Patent Document EP 0 690 802 B1, a secondary suspension for a rail vehicle is known which is constructed in the manner of a hydropneumatic suspension. The secondary suspension is achieved by a hydraulic cylinder whose pressure chamber is connected with a hydropneumatic pressure accumulator. By the gas volume of the hydropneumatic pressure accumulator, a vertical spring effect is achieved. Furthermore, the hydraulic cylinder is equipped with a pendulum support which forms a part of a piston rod which having a joint at an upper end. During transverse movements, the pendulum support swings out, its end rolling on a corresponding surface. Since the radius of the end surface of the pendulum support is larger than the distance of the joint from its supporting surface, a restoring moment takes place during transverse movements which, as a result of the constant distance of the joint from the supporting surface, is independent of the spring excursion.
It is generally known to use conventional steel springs for the secondary suspension in the simplest case, in addition to a pneumatic suspension or hydropneumatic suspension. The superstructure is normally cushioned with respect to the bogie by two passive spring elements, in which case the bogie normally carries a pair of wheel axles which establish the contact with the rail.
However, when a secondary suspension is constructed by steel springs as passive spring elements, the problem arises that the superstructure level may change as a function of the loading. In the present disclosure, the superstructure level is the vertical level of the superstructure relative to the bogie or to the ground.
From European Patent Document EP 0 663 877 B1, a system for the secondary suspension is known which avoids the above-noted problem in that no steel springs are used for the secondary suspension. The secondary suspension is implemented by a hydropneumatic spring unit. The hydropneumatic spring unit consists of a spring leg and of a hydropneumatic pressure accumulator. These assemblies carry out the function of cushioning the superstructure as well as the function of damping the spring excursions. The spring leg is fastened on the superstructure and on the bogie. During a spring excursion, the piston in the spring leg displaces a defined oil volume. In the hydropneumatic pressure accumulator connected with the spring leg, this oil volume acts against a gas cushion which is separated from the oil volume by a membrane and is therefore used as a springy element. The hydraulic fluid, as the liquid column, therefore takes over the function of the power transmission. Vehicle vibrations during the travel are damped by the nozzles housed in a nozzle block. As the load of the superstructure increases, the gas volume in the hydropneumatic accumulators is compressed. Without any level control system, this would result in a lowering of the superstructure, as in the case of the above-described passive spring element. However, in order to avoid this lowering, the reduction of the gas volume has to be compensated by feeding a corresponding amount of hydraulic fluid. For this purpose, the level control system is provided which carries out this compensation as a function of the distance between the superstructure and the bogie measured by a level sensor. The controlling of level changes takes place continuously and with little time delay while the vehicle is stopped. During the travel, the mean vehicle level is also continuously monitored and compensated.
In certain application cases, it is defined that, in addition to a raised traveling level NF, the superstructure also has to take up a station platform level NB which is below it and which, in a lowered position of the superstructure matches the door steps of the rail vehicles with the height of the station platform, so that an entering and exiting becomes possible without steps. Furthermore, it has to be provided that, despite such a lowered station platform level NB, in the case of a system failure in the station, the superstructure of the rail vehicle, while being operated independently and manually, can also be brought to an emergency level NN situated above the platform level, for resuming the travel. Furthermore, it is to be provided that, in the event of a system failure, the superstructure of the rail vehicle, during the travel, is not lowered from the raised traveling level NF to below the emergency level NN.
Despite the system failure, this emergency level NN situated between the lowered station platform level NB and the raised traveling level NF permits an at least slow continued traveling of the rail vehicle.
In the case of the known system for the secondary suspension with an active level control system, an emergency level NN, starting from a traveling level NF, however, can be adjusted only if sufficient storage pressure is still present in the storage accumulator and the assigned valve is operated manually. Thus, an emergency level NN does not have to be ensured under all circumstances.
The present disclosure provides a system for the secondary suspension by which, despite a system failure, under all conditions, the superstructure, when stopped, can take up an emergency level NN from a lowered station platform level NB and, in the event of system failure during travel, the superstructure is not lowered below the emergency level NN from the raised traveling level NF.
Thus, according to the present disclosure, a secondary suspension system for a rail vehicle includes a superstructure and a bogie arranged below the superstructure. Also included is a hydropneumatic spring unit located between the superstructure and the bogie. The hydropneumatic spring unit provides, in a normal operation, at least one raised traveling level for the superstructure and a lowered platform level for the superstructure that is lower than the at least one raised traveling level. Further included is at least one emergency spring cylinder, wherein when the system fails, the at least one emergency spring cylinder provides an emergency spring level situated between the at least one raised traveling level and the lowered platform level.
The present disclosure includes the technical teaching that, by a hydropneumatic spring unit being used as an active spring element in the normal operation, in addition to the raised traveling level NF, a lowered station platform level NB can be adjusted for the superstructure. Additionally, at least one emergency spring cylinder is provided which, when the system fails, ensures an emergency operation by an emergency spring level NN situated in-between the traveling level NF and the lowered platform level NB. On the one hand, the emergency spring level NN, in the event of a system failure, can be adjusted by an automatic moving-out of the emergency spring cylinder. On the other hand, it is also conceivable, as an alternative, that the emergency spring level NN occurs in the event of a system failure by the already moved-out emergency spring cylinder which therefore is already in readiness.
According to the present disclosure, having an active secondary suspension with respect to the flexible adjustment of different superstructure levels connected with a passively functioning emergency operation permits at least a slow continued traveling of the rail vehicle. In principle, the emergency suspension is automatically activated when the system pressure decreases. During the stoppage times, that is, in the area of the station stop, this has the effect that the superstructure can reach a higher emergency spring level NN from the lower station platform level NB.
According to a an embodiment of the present disclosure, the emergency spring cylinder includes a hydraulic tension cylinder and a piston, and the tension cylinder can be moved out by a pressure spring. The force exercised by the pressure spring in the tensioned condition upon the tension cylinder is stored by a rearward admission of pressure medium to the tension cylinder. When this rearward pressure decreases, the piston or the tension cylinder carries out the move-out motion as a result of the now predominant spring force.
A space-saving arrangement may be achieved in that the pressure spring is produced of steel in the manner of a coil spring which coaxially surrounds the tension cylinder. As a result of this arrangement of the pressure spring, which is exposed to the outside, the applicable spring force can be maximized because of the large diameter. Simultaneously, the components of the tension cylinder, which can be moved relative to one another, are protected by the pressure spring surrounding them.
With respect to the flow of force, the emergency spring cylinder can be connected in parallel or in series to the hydropneumatic spring unit.
In the case of a parallel connection, the emergency spring cylinder can be arranged to be acting locally next to the hydropneumatic spring unit between the superstructure and the bogie. The side-by-side arrangement, in the case of existing secondary suspensions with a hydropneumatic spring unit as an active spring element, may allow a retrofitting to take place in a simple manner by adding the emergency spring cylinder in order to permit an emergency operation or the concerned rail vehicles.
As an alternative, it is also conceivable to have an embodiment configured such that the emergency spring cylinder coaxially surrounds the hydropneumatic spring unit and is disengaged in the normal operation, with the emergency spring cylinder being used in the emergency operation. This embodiment of a parallel connection represents a space-saving solution because little space is required for installing the secondary suspension, according to the present disclosure. Also, in the emergency operation, parts of the hydropneumatic spring unit continue to participate in the power transmission. That is, they do not remain completely unutilized.
In addition, for the just-noted embodiment, for the emergency operation, the hydropneumatic spring unit is vertically guided by a coaxial upper pin via a corresponding recess on a side of the superstructure. It is also conceivable to arrange the guiding elements in a reverse manner, so that a pin is arranged on a side of the undercarriage, which pin is vertically guided in a corresponding recess on a side of the hydropneumatic spring unit or the like.
A series connection of the emergency spring cylinder and the hydropneumatic spring unit according to the flow of force is possible, in that both units are arranged behind one another in the flow of force and therefore act simultaneously. For reaching the lowered station platform level NB for the superstructure, an additional action upon the tension cylinder takes place in order to compress the pressure spring. In this embodiment, a difference is made in the normal operation between the operation when traveling and the operation when stopped, that is, at the station platform. During travel, the hydropneumatic spring unit acts in series with the steel spring of the tension cylinder; that is, the tension cylinder is pressureless and the steel spring can oscillate. In contrast, at the station platform, the steel spring is compressed by the action upon the tension cylinder in order to implement a lowering of the rail vehicle to the station platform level NB. If the hydropneumatic spring unit fails (system failure), the steel spring takes over the secondary suspension. The flow of force is created by the direct contact of the piston and the cylinder of the hydropneumatic spring unit in the end stop position, whereby the spring rigidity is also increased in the case of a corresponding design. The transverse suspension is maintained as a result of the series arrangement. In contrast to the above-described embodiments, here the steel spring of the emergency suspension is always positioned correctly, so that there are no take-over problems with respect to the latter.
The automatic moving-out of the piston of the emergency spring cylinder takes place as a result of a pressure drop. As an alternative, it is also conceivable that, in the normal operation, the piston of the emergency spring cylinder remains moved-out while being disengaged. The hydropneumatic spring unit ensures the traveling level NF, and that, after an activating of unlocking devices, the piston can at least partially be lowered inside a pot-shaped cylinder housing surrounding it. This has the effect that also the lowered station platform level NB can be reached. In the event of a system failure during the travel, the normally closed unlocking devices ensure the moved-out position of the piston of the emergency spring cylinder so that the emergency level NN is ensured by way of the emergency spring cylinder. In the event of a system failure in the station, that is, during a stoppage, pressure has to be applied by way of another circuit. This can be achieved by a manual operation or by the pressure medium stored in an additional storage device.
In the first-described embodiment, the piston of the emergency spring cylinder should include at least one piston sleeve telescopically displaceable against a spring force into the piston in order to ensure the spring deflection along the required spring travel. A high spring force can be generated in that an elastomer element is coaxially surrounded by a coil spring made of spring steel. In this embodiment, high spring forces can be implemented for a secondary suspension so that a multiple arrangement of emergency spring cylinders for the secondary suspension for ensuring the emergency operation can possibly be avoided.
It may also be conceivable to completely eliminate the hydropneumatic spring unit in this embodiment. The reason is that the emergency spring cylinder of this embodiment can also be used directly for the level control by the admission of pressure medium to a pressure chamber. This will then be a type of vertically adjustable emergency spring which is locked in the moved-out position of the piston and to this extent takes over the function of the secondary spring in the normal operation as well as of the emergency spring in the emergency operation.
The system according to the present disclosure for the secondary suspension includes a hydropneumatic spring unit as well as an emergency spring cylinder which can be acted upon by a pressure medium. The system can be operated by a single hydraulic circuit or by two separate hydraulic circuits. In the case of a single hydraulic circuit, the hydropneumatic spring unit as well as the emergency spring cylinder can be supplied with pressure medium therefrom. However, the minimal dynamic pressure in a hydraulic accumulator should be sufficiently dimensioned such that the pressure spring of the emergency spring cylinder can be kept in the compressed condition. In contrast, in the case of two hydraulic circuits, one hydraulic circuit is assigned to the hydropneumatic spring unit, and the other hydraulic circuit is assigned to the emergency spring cylinder. The two hydraulic circuits allow for different operating pressures to be a provided for the two circuits, which results in freedom with respect to the design and dimensioning of the pressure medium aggregates.
The hydropneumatic spring unit may comprise a pendulum support so that transverse movements between the superstructure and the bogie are permitted and restoring forces are applied for centering the superstructure.
In order to implement an active level control between the raised traveling level NF and the lowered station platform level NB, a level sensor is provided for measuring the actual distance between the superstructure and the bogie. The level sensor operates as an actual value generator and transmits the electrical measuring signals to an electronic control unit comprising a regulating unit which generates corresponding adjusting signals for the valve control of the hydraulic circuits based on defined desired values, so that the desired superstructure level can be adjusted. This normally takes place via the hydropneumatic spring unit.
Other aspects of the present disclosure will become apparent from the following descriptions when considered in conjunction with the accompanying drawings.